The Details of Good and Bad Stone Masonry

Some of the most important specifics missing from the video have a lot to do with what makes an installation look good. It might seem odd to have to explain some of this, but it’s not as obvious as you might think. Once you know what a good natural stone veneer installation should look like, it’s something you will notice forever when looking at projects that include building stone veneer.

The first thing is the mortar joint. You’d think it’s the stone, but really it’s the mortar joint that can make all the difference. A mortar joint is a key element. Whether it’s drystacked, raked back, flush, or overgrouted, a bad mortar joint stands out and can make the entire project look bad – stone and all.

What, you ask, is a bad mortar joint? It can come in several forms. One is inconsistent size. If you’re doing a typical mortar joint, the average installation will have roughly a 1/2 inch joint. Even with bad stone, a consistent mortar joint can make all the difference in the world.

The picture above is an extreme example and has more than just bad mortar joints going on, but you get the idea. Notice how the joint is inconsistent? It goes from tight to spaced. A diamond saw might have helped save the project, but as you can see, the joint just doesn’t look right. After the contractor was fired from this project, a different mason removed and re-installed the stone. See what a difference it made!

Another thing to consider is the style of stone you are installing. It may not look like it, but there is a method to the madness in the installation. There is actually a pattern for the different stone types.

An Ashlar Line pattern of installation is sometimes referred to as a 2:1 pattern. This is as it sounds, two smaller stones to one bigger stone.

The above swatch image of our Chilton Cambrian Blend illustrates a 2:1 pattern. It’s a product in our Ashlar Line, but many different stone product types can be installed this way – with two stones butting up to one and creating a vertical joint. This does a couple of things. First, by installing stone pieces in this way, it breaks up the joints so they don’t run into each other. This also helps keep the horizontal joints from forming long, coursed runs. The other thing to notice is the variations on the vertical joints. A good rule of thumb is to have a minimum of four inches between vertical joints to keep them from running a long distance up and down; they should always be staggered.

The next type of stone masonry installation is what we call a Mosaic installation. The same rules pretty much apply here with joint sizes, and not having the joints running too long vertical or horizontal. The one difference with a Mosaic Line pattern (sometimes referred to as irregular) is you have to watch “the crotch” of the stones.

Basically, when the stones line up with each other, what you want to watch for is a big triangle showing up in the joint because the stone shapes don’t line up well. The above swatch photo for Blue Ridge River Rock is a pretty good stone masonry installation. Areas where the crotches of the stone pieces are a little bigger than they probably should be are indicated by white triangles. You can see the joint between those stones is a little bigger than the rest. It’s not bad – just not as good as it could be.

Image 1 shows a standard-type mortar joint with a gray mortar. This type of joint is also often called a raked joint. There are a lot of ways to accomplished this finish, from using a piece of wood or a tuck pointer. Once the mortar is thumbprint hard (pictured earlier in this post – a consistency where you can press into it and see your actual thumb print) you would use the tool of choice to scrape the mortar out about a 1/4 – 1/2 inch back. Then you use a stiff brush to clean the bits of excess mortar off. This also helps seal up the joints and prevent hairline cracks.

Image 4 is a drystacked installation. As you can see, there is almost no mortar showing. One advantage of a drystack joint is there is no waiting for the mortar to dry, so you can work on installing it right up to the end of the day. The most difficult part of this install is the effort it takes to make the stone look good. It is important to have a grinder or diamond saw to help grind down high spots. This will help the stones fit tighter together. You do have to be a little more cautious when using this installation for exterior applications as water can get behind the stone much easier, making it even more important for you to incorporate our weep system or use Laticrete’s MVIS products.